Metallic cans, glass bottles, containers and molded articles formed of a thermoplastic resin, and the like have been used as packing materials for medical drugs, beverages, foods chemical products and the like. Among these, containers and molded articles formed of a thermoplastic resin are superior in lightweight property, moldability, packaging productivity, such as heat sealing property, and cost, and thus have been used in the largest quantity. In general, however, containers and molded articles formed of a thermoplastic resin undergo oxygen permeation in nonnegligible extent through a container wall, which causes a problem in storageability of contents, although they are excellent as a packaging material.
For preventing oxygen permeation from the outside of the container, the container or molded article of a thermoplastic resin is formed to have a container wall having a multilayer structure, in which at least one layer thereof is an oxygen barrier layer, such as poly-m-xylylene adipamide (which is hereinafter referred to as “N-MXD6”), an ethylene-vinyl alcohol copolymer, polyacrylonitrile and an aluminum foil. However, the container fails to prevent not only invasion of a slight amount of oxygen from the outside of the container, but also deterioration of the contents of the container that are sensitive to oxygen, such as beer, with oxygen remaining in the container.
An oxygen absorbent has been steadily used for removing oxygen in a container. For example, Patent Documents 1 and 2 disclose an oxygen absorbing multilayer material and an oxygen absorbing film containing an oxygen absorbent, such as iron powder, dispersed in a resin. Patent Document 3 discloses an oxygen scavenging barrier for packaging that absorbs oxygen inside and outside a container, in which the oxygen scavenging barrier contains a polymer material, such as polyamide, to which a metallic catalyst, such as cobalt, is added. Patent Document 4 discloses a product containing an oxygen removing layer containing an ethylenic unsaturated compound, such as polybutadiene, and a transition metal catalyst, such as cobalt, and an oxygen barrier layer, such as polyamide.